/Engine/Plugins/Experimental/GameFeatures/Source/GameFeatures/Public/GameFeaturesSubsystem.h
Call this if your observer has an asynchronous action to complete as part of shutdown, and invoke the returned delegate when you are done (on the game thread!)
FSimpleDelegate PauseDeactivationUntilComplete ( [FString](API\Runtime\Core\Containers\FString) InPauserTag )